Assay a statistically adequate number of sera from patients with breast cancer, benign breast disease, and normal volunteers for IC's employing multiple techniques for IC detection and quantitation which have been developed in and are currently in operation in our laboratory. Our multiple techniques will permit differentiation of soluble and insoluble IC's and of complement bearing and IgG-Fc accessible IC's. To correlate presence or absence, or levels where applicable, of individual IC subpopilations with tumor progression, response to therapeutic intervention, and clinical course otherwise. Data will be analyzed according to clinical stage of the patient, histologic type of the tumor, histology of regional lymph nodes, ovarian and other hormonal status of the patient, and the presence or absence of estrogen receptors on tumor cells.